Śatapatha Brāhmaṇa ("of a hundred paths") 6.7.1.26

6.7.1.26

yadvevainanamiṇḍvābhyām parigṛhṇāti | asau vā āditya eṣo 'gnirimā u lokāviṇḍve amum tadādityamābhyāṃ lokābhyām parigṛhṇāti tasmādeṣa ābhyāṃ lokābhyām parigṛhītaḥ parimaṇḍale bhavataḥ parimaṇḍalau hīmau lokau mauñje trivṛtī tasyokto bandhurmṛdā digdhe tasyo evokto 'tho anatidāhāya

And, again, why he takes hold of him by means of two pads,--he, Agni, is yonder sun, and the two pads are these two worlds: he thus encompasses yonder sun by these two worlds, and hence he is encompassed by these two worlds. They are round, for these two worlds are round; of reed-grass, triply wound,--the significance of this has been told;--and smeared with clay,--(the significance) of this also has been told, but it also serves to keep them from taking fire.